1. Field of the Invention
The present invention relates to an apparatus for vaporizing liquids, and more particularly, to an apparatus for continuous vaporization of large quantities of multicomponent liquids.
2. Description of the Prior Art
In sterilization processes, items to be sterilized may be contacted with a vapor phase of a multicomponent sterilant. Such vapor phase sterilants are provided by vaporizing a liquid phase multicomponent sterilant. However, such multicomponent sterilants are often difficult to vaporize due to the difference in vaporization temperatures of the various components. If care is not exercised, preferential vaporization will occur resulting in a vapor phase of different concentration than the liquid phase which may jeopardize the efficacy of the sterilization process.
One method of vaporizing a multicomponent liquid is disclosed in U.S. Pat. No. 4,642,165 to Bier which issued on Feb. 10, 1987. In that method, a predetermined increment of the liquid is metered onto a heated surface of a vaporization chamber. Each increment is substantially instantaneously vaporized before the next increment is introduced to the surface. The vapor then passes into a vacuum chamber.
The Bier method is useful for vaporizing small quantities of liquid on the order of eight grams/minute. However, applications such as the sterilization of an entire room, require much greater quantities, on the order of one hundred and twenty grams/minute. When such large quantities of liquid are introduced into the Bier apparatus, the vaporizer loses heat faster than it can be replaced. Soon the vaporizer cannot vaporize all of the liquid, puddles form, and the vaporizer floods. A vaporizer using the Bier method is incapable of vaporizing a large continuous stream of liquid thus making it incapable of meeting large scale sterilization needs.
Another method of vaporizing a multicomponent liquid is disclosed in U.S. Pat. No. 4,424,189 to Hick which issued on Jan. 3, 1984. In that patent, a heating coil is inserted into an open-topped container. A sterilizing agent is sprayed onto the heating coil and vaporizes upon contact with the coil. Clearly, such a method which requires inserting the heating coil into the item to be sterilized is not suitable for producing a large stream of vaporized sterilant. Additionally, the heating element may act as a catalyst for degrading the vaporized sterilant. A spiral heating element such as that used in the Hick's patent presents a large surface area which exacerbates that problem.
Accordingly, there is a need for an apparatus which is capable of vaporizing large quantities of a multicomponent liquid. That is especially true for chemical sterilants, as distinguished from moist beat sterilants such as steam. The chemical vapors may not always be stable. Vapor phase hydrogen peroxide, for example, degrades into water vapor and oxygen. Thus, because current vaporizers are not capable of quickly vaporizing large quantities of liquid phase hydrogen peroxide, when a large enclosure is involved, the hydrogen peroxide vapors degrade before a desired concentration can be achieved.